public static ChasingGroup Instance(float speed, float radius, float targetRadius, string group)
 {
     var key = new Tuple<float, float, float, string>(speed, radius, targetRadius, group);
     ChasingGroup ret;
     if (!instances.TryGetValue(key, out ret))
         ret = instances[key] = new ChasingGroup(speed, radius, targetRadius, group);
     return ret;
 }
        public static ChasingGroup Instance(float speed, float radius, float targetRadius, string group)
        {
            var          key = new Tuple <float, float, float, string>(speed, radius, targetRadius, group);
            ChasingGroup ret;

            if (!instances.TryGetValue(key, out ret))
            {
                ret = instances[key] = new ChasingGroup(speed, radius, targetRadius, group);
            }
            return(ret);
        }